This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A031225 #4 Mar 30 2012 18:56:21 %S A031225 1,2,3,4,5,7,1,11,13,15,10,19,2,23,25,12,22,31,3,35,4,14,24,34,45,5, %T A031225 51,54,57,50,7,8,69,72,75,9,18,1,87,90,11,28,99,102,105,73,13,114,117, %U A031225 120,76,15,129,132,53,68,17,10,113,128,82,19,20 %N A031225 a(n)=least k such that base 5 representation of n begins at s(k), where s=A031219. %K A031225 nonn %O A031225 1,2 %A A031225 _Clark Kimberling_